ANTHROPIC_DEFAULT_FABLE_MODEL
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.170, including the newest one read.
What it is
Model ID that the fable alias resolves to, and the ID Claude Code recognizes as Fable 5 for [automatic model fallback](/docs/en/model-config#automatic-model-fallback) on third-party providers. See [Model configuration](/docs/en/model-config#environment-variables)
Anthropic's own wording. Read off Environment variables, captured 2026-08-28.
Presence across releases
| Releases | Reading | Declared type | Default |
|---|---|---|---|
| 2.1.245 – 2.1.250 5 releases | never mined | — | — |
| 2.1.170 – 2.1.243 66 releases | in the build | str | — |
A row reading never mined is a release with no archived bundle behind it. Nothing was read out of it, so nothing here says whether the name was in it. A declared type or a default is only ever what that release's own bundle stated.
Changelog entries naming it
No changelog entry here has ever named it. That is a statement about what has been written, not about the name: it has been in the build since v2.1.170 without anybody writing a line about it.
Documentation pages
- Environment variables reference table Claude Code CLI
- Claude Code on Claude Platform on AWS mentions it Claude Code CLI
- Model configuration mentions it Claude Code CLI
- Enterprise deployment overview mentions it Claude Code CLI
A reference table page is one whose own table defines this name, and it is where the description above came from. A page that mentions it carries the name somewhere in its text and may say nothing about it at all. Every page carrying it.
Names beside it
Every environment variable in the inventory starting anthropic_default_fable, up to twelve of them.
ANTHROPIC_DEFAULT_FABLE_MODEL_DESCRIPTIONDisplay description for the pinned Fable model in the /model picker. Defaults to Custom Fable model when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) 2.1.170
ANTHROPIC_DEFAULT_FABLE_MODEL_NAMEDisplay name for the pinned Fable model in the /model picker. Defaults to the model ID when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) 2.1.170
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the environment variable does. All environment variables.